Plugged spray nozzle detection using radio-frequency transmissions

ABSTRACT

An agricultural sprayer includes at least one nozzle configure to receive a fluid and direct atomized fluid to an agricultural surface in a dispersal area. A radio-frequency (RF) transmitter is disposed to generate an RF signal that passes through the dispersal area. The RF signal is detectably changed when interacting with droplets of the atomized fluid. A first RF receiver is disposed to receive the RF signal after the RF signal passes through the dispersal area and provides an output indicative of the RF signal. A controller is coupled to the first RF receiver and is configured to detect plugging of the at least one nozzle based on the output of the first RF receiver.

FIELD OF THE DESCRIPTION

This invention relates to a spraying apparatus for an agriculturalsprayer. More specifically, the invention relates to systems and methodsfor detecting full or partial plugging of a spray nozzle of anagricultural sprayer.

BACKGROUND

Agricultural spraying systems are known. Such systems typically includea fluid line or conduit mounted on a foldable, hinged, or retractableand extendible boom. The fluid line is coupled to one or more spraynozzles mounted along the boom. Each spray nozzle is configured toreceive the fluid and direct atomized fluid to a crop or field duringapplication.

Spraying operations are generally intended to distribute a product (e.g.fertilizer, pesticides, etc.) evenly over an agricultural surface, suchas a field or crop. Properly functioning spray nozzles ensure thatdispersal of the product occurs evenly and is important to ensure cropyields.

SUMMARY

An agricultural sprayer includes at least one nozzle configure toreceive a fluid and direct atomized fluid to an agricultural surface ina dispersal area. A radio-frequency (RF) transmitter is disposed togenerate an RF signal that passes through the dispersal area. The RFsignal is detectably changed when interacting with droplets of theatomized fluid. A first RF receiver is disposed to receive the RF signalafter the RF signal passes through the dispersal area and provides anoutput indicative of the RF signal. A controller is coupled to the firstRF receiver and is configured to detect plugging of the at least onenozzle based on the output of the first RF receiver.

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter. The claimed subject matter is not limited to implementationsthat solve any or all disadvantages noted in the background.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an agricultural field sprayer with which embodimentsdescribed herein are particularly useful.

FIGS. 2A-2C illustrate example spray patterns from spray nozzles withina spray system.

FIGS. 3A and 3B illustrate systems for detecting spray nozzle pluggingin accordance with an embodiment of the present invention.

FIGS. 4A and 4B illustrate a multi-nozzle system employing RF-basedplugging detection in accordance with an embodiment of the presentinvention.

FIGS. 5A and 5B illustrate a multi-nozzle system employing RF-basedplugging detection in accordance with another embodiment of the presentinvention.

FIG. 6 is a flow diagram of a method of detecting a plugged nozzle usingRF transmissions in accordance with an embodiment of the presentinvention.

FIG. 7 illustrates an environment in which embodiments described hereinare particularly useful.

DETAILED DESCRIPTION

Embodiments described herein generally employ radio-frequency (RF)transmissions to detect a change in output from one or more nozzles. Asthe radio-frequency energy of the transmission passes through thedroplets of a spray nozzle, the RF signal is changed in a detectableway. An RF receiver, configured to detect the RF signal that has passedthrough the spray, provides an output that is monitored to provide spraynozzle diagnostic indications. As used herein, radio-frequency (RF) isdefined to mean electromagnetic energy having a frequency in the rangefrom about 3 kHz to 300 GHz.

FIG. 1 illustrates an agricultural field sprayer with which embodimentsdescribed herein are particularly useful. FIG. 1 illustrates anagricultural environment 150 in which a tractor 160 is coupled to, andpulls, a towed sprayer 162. Towed sprayer 162 includes spray system 170,which has a tank 172 containing a liquid that is being applied to field180. Tank 172 is coupled to boom 174, and the product is delivered tospray nozzles 176, which are spaced apart along boom 174. It isimportant, in environment 150, that product is evenly distributed acrossfield 180. For example, if fertilizer is unevenly applied, it is wastedin areas of over-application, and areas of under-application can seereduced yields.

FIGS. 2A-2C illustrate example spray patterns from spray nozzles withina spray system. FIG. 2A is a diagrammatic representation of an examplespray system 200 having a number of spray nozzles 210 spaced apart alongboom 202. Each spray nozzle 210 generates a dispersal 220 of sprayed orotherwise atomized product. As illustrated in FIG. 2A, spray nozzle 215is at least partially plugged, creating an overlap area 212, wheredistributed product is overapplied, and an uncovered area 214, where noproduct is applied.

FIGS. 2B and 2C illustrate a contrast between a properly functioningspray system 250 and a spray system 270 that has a plugged spray nozzle240. As illustrated in FIG. 2C, because spray nozzle 240 is fullyplugged, area 242 will receive no dispersed product. This can result inlower yield for the portion of the field covered by area 242.Additionally, a plugged spray nozzle also impacts the spray quality asthe target application rate is not achieved for a portion of the field.

FIGS. 3A and 3B illustrate systems for detecting spray nozzle pluggingin accordance with an embodiment of the present invention. FIG. 3A is adiagrammatic view of RF-based plugged nozzle detection in accordancewith one embodiment. Nozzle 310, when functioning properly, emitsproduct in a predictable dispersal pattern 320. An RF transmission 315,sent from signal transmitter 312, passes through dispersal pattern 320,and is detected by RF signal detector 314. The RF signal 315 isdetectably changed as it passes through dispersal pattern 320. Thisdetectable change is generally a change in the attenuation of thesignal. Thus, controller 317 coupled to transmitter 312 and receiver314, can detect a change in the received signal by monitoring one ormore characteristics of the RF signal (such as amplitude) using receiver314. In this way, controller 317 detects changes indicative of pluggingand provides a useful ability to diagnose, and/or correct, a pluggednozzle quickly. Controller 317 can be any suitable logic or circuitarrangements that are able to receive an output signal from receiver 314and analyze the output to detect partial or full nozzle plugging. In oneembodiment, controller 317 is a microprocessor. Controller 317 may beseparate from each of transmitter 312 and receiver 314 or it may becombined with either of transmitter 312 or receiver 314. Advantageously,the techniques described herein employ RF energy to detect spray nozzleplugging and this do not employ optical techniques, which can bedistorted or otherwise affected by dirt, dust, darkness or othervariables.

One example of electromagnetic energy being affected by passing throughdroplets of liquid is known as rain fade. Rain fade describes theattenuation of the RF signal as it passes through and is at leastpartially absorbed by atmospheric snow, ice or rain. Rain fade isparticularly evident at RF frequencies above 11 GHz and is typically aquantity that is compensated for in electromagnetic transmissions. Oneparticularly useful range of RF signals for embodiments described hereinis a frequency range from about 7 GHz to about 55 GHz.

FIG. 3B illustrates a spray system 350 for a plurality of nozzles 360mounted on boom 352. In the illustrated example, each nozzle 360 ispaired with an RF signal transmitter (not shown) that emits a signal362. In one example, each transmitter transmits a signal of the sameamplitude but with a different frequency to that the RF receiver candifferentiate the various signals. The RF transmitters can be positionedclose to each of nozzles 360, such that each RF signal will pass throughthe dispersal pattern of its respective nozzle and be received by RFsignal receiver 314. For example, the signal transmitters can be placednext to each nozzle 360, as well as above or below each nozzle 360 aslong as the RF signal passes through the dispersal pattern of therespective nozzle. Thus, the signal transmitters can be mounted directlyto boom 352, or to each of nozzles 360, or in other appropriatelocations.

In one embodiment, RF receiver 314 is configured to substantiallysimultaneously receive RF signals relative to each of nozzles 360.However, it is also contemplated that RF receiver 314 may be configuredto alternatively receive and analyze incoming RF signals relative toeach nozzle 360 sequentially. The system, thus is able to provide asubstantially real-time indication of the current efficacy of eachnozzle during operation.

FIG. 4A illustrates a multi-nozzle spray system employing RF-basedplugging detection in accordance with an embodiment of the presentinvention. System 400 includes a boom 402 coupled to a plurality ofmulti-nozzle bodies 410. In one example, multi-nozzle bodies 410 areused to deliver effective coverage over more area in less time. Usingmultiple nozzles allow an increase in productivity by better toleratingchanges in spray speed. The group of nozzles can be used to deliver asingle product at varying rates depending on how many individual nozzlesare engaged. Additionally, the utilization of various nozzles canprovide better placement precision of the product. In one example,multi-nozzle bodies 410 are those sold in relation to the tradedesignation ExactApply™ Nozzle Control, available from John DeereCorporation, of Moline, Ill.

As shown, each multi-nozzle body 410 is configured to mount a pluralityof spray nozzles, such as first nozzle 412 and a second nozzle 414.First nozzle 412 and second nozzle 414 are diametrically opposite oneanother on multi-nozzle body 410. As illustrated in FIG. 4A, amulti-nozzle body 410 can be coupled to more than two nozzles; forexample 4A shows five nozzles for each multi-nozzle body 410. Eachmulti-nozzle body 410 also includes, or is coupled to, an RF transmitter430 that is configured to emit an RF signal. In one example, the RFsignal is omnidirectional emanating outwardly from the center ofmulti-nozzle body 410. As can be appreciated, the RF signal will passthrough the dispersal patterns of any individual nozzles that areengaged. The RF signal passing through the droplets of each dispersalpattern will be attenuated, or otherwise affected. An RF receiverpositioned to detect the RF signal after passing through such adispersal pattern is then used to detect whether a particular nozzle'spattern has changed.

FIG. 4B illustrates an agricultural sprayer 550 with a pair of RFreceivers 560, 570 to receive RF signals relative to multiple individualnozzles of a multi-nozzle body 410 in accordance with an embodiment ofthe present invention. As illustrated in FIG. 4B, first RF receiver 560is mounted near solution tank 554, and second RF receiver 570 is locatedon the back side of a boom 552. Both first and second receivers 560,570, receive the same signal from each multi-nozzle body RF transmitter430. However, the signal received by first RF receiver 560 will beattenuated by the nozzle 412 (shown in FIG. 4A) while the signalreceived by second RF receiver 570 will be attenuated by nozzle 414(shown in FIG. 4A). First and second receivers 560, 570 are coupled to asuitable controller, such as a controller of the agricultural machine,which analyzes the received signals to provide a plugging indicationrelative to the various nozzles, such as nozzles 412, and 414. Thisanalysis may be as simple as merely comparing the two signals, such thatany difference between the two signals can be used to indicate whichnozzle of the pair of nozzles is plugged, either partially or fully.

FIGS. 5A and 5B illustrate a multi-nozzle system employing RF-basedplugging detection in accordance with another embodiment of the presentinvention. FIG. 5A is a bottom view of a multi-nozzle body having aplurality of individual RF transmitters, where each individual nozzle610 of the multi-nozzle assembly has an associated RF transmitter 620.When only a subset set of nozzles 610 is active (for example, one pairof nozzles 610), only a subset of the associated transmitters 620 arealso active. The RF signal transmitted by each RF transmitter 620 isattenuated by surrounding spray nozzles 610.

In embodiments where multiple RF transmitters 620 are used, any suitabletechnique for disambiguating the signals can be employed. For example,one RF transmitter 620 may operate in a first frequency range, whileanother RF transmitter 620 may operate in a second frequency range thatdoes not overlap the first frequency range. Additionally, oralternatively, the different RF transmitters 620 may provide differentmodulation of their respective RF signals. Further still, the differentRF transmitters 620 may be operated in sequence such that only a singleRF transmitter 620 is operating at any given time.

FIG. 5B illustrates an agricultural sprayer 500 with RF receiver 510mounted proximate a solution tank and configured to detect signals fromthe various RF transmitters 620 (shown in FIG. 5A). In one embodiment, acontroller coupled to RF receiver 510 is configured to compare data fromeach nozzle with default data stored in the controller, or in anothersuitable location, that indicates normal nozzle operation. Based on thecomparison to the default data, the controller can determine if aparticular nozzle or pair of nozzles has partial or full plugging.

FIG. 6 illustrates a flow diagram of a method of detecting a pluggedspray nozzle in accordance with an embodiment of the present invention.Method 700 can be used to detect a partial or fully plugged status of anozzle on an agricultural sprayer. Method 700 can also be used with atleast some of the single and multi-nozzle systems described herein.

Method 700 begins at block 705 where an RF signal is generated andpasses through a dispersal area of at least one nozzle.

At block 710, the RF signal is received using an RF receiver, such asreceiver 510. Next, at block 720, the received RF signal is analyzed.Analyzing the received RF signal, can include comparing the signal witha standard signal obtained and stored during known-good sprayingconditions, as indicated in block 712. The standard can include amanufacturer-provided range of acceptable RF signals, or an indicationof RF signals that indicate partial or complete plugging. Analyzing thereceived RF signal can additionally or alternatively include comparingthe received signal with one or more received signals relative to othernozzles, as indicated in block 714. For example, using an average of aset of received RF signals can indicate that one or more nozzles in aset of nozzles is plugged, for example because the RF signal receivedfrom the plugged nozzle is different from the average in a statisticallysignificant way. Historical data for a nozzle can also be used to detectfull or partial plugging, as indicated in block 716. For example, areceived RF signal will change as plugging is experienced, and the RFsignal travels through a thinner, or non-existent spray.

At block 730, if a partial or fully plugged sensor is detected, method700 proceeds to block 740 where an indication of plugging is provided.However, in the event that no plugging is detected for a particularnozzle, method 700 returns to block 705, and thus repeats.

At block 740, an indication of a plugged nozzle status is generated andsent. For example, an indication can be sent directly to an operator, asindicated in block 742, for example as an audible or visual alert.Additionally, or alternatively, a notification can be provided to anoperator's device, such as a mobile phone. The indication can also besent directly to the agricultural sprayer, as indicated in block 744,for remedial action, such as automatically switching to a different pairof active nozzles in a multi-nozzle assembly.

FIG. 7 illustrates an environment in which embodiments of the presentinvention are particularly useful. Sprayer system 810 is located withinenvironment 800, and may be mounted to an agricultural vehicle, or towedby an agricultural vehicle, as illustrated in FIG. 1. Sprayer system 810has one or more nozzles 802, either mounted directly to a boom, or to anozzle body. Each nozzle 802 is associated with an RF transmitter 804.The signals generated by RF transmitter(s) 804 are configured to passthrough respective dispersal areas of respective nozzles 802 and beattenuated or otherwise distorted by droplets of liquid in the dispersalarea. The distorted RF signal is then detected by an RF receiver 806.Sprayer system 810 may include a single RF receiver 806 (such asdescribed above with respect to FIGS. 5A and 5B) configured to receivesignals alternatively from different RF transmitters 804 or sprayersystem 810 may employ two or more RF receivers 806 (such as describedabove with respect to FIGS. 4A and 4B).

Environment 800 also includes an RF-based plug detection system 820,which may be located locally, for example as part of a computing unitwithin an agricultural vehicle, or remotely from an agriculturalvehicle, for example within a separate computing system. RF-based plugdetection system 820 includes storage component 830, which stores nozzledata 832, obtained from a plurality of nozzles 802, for example. Nozzledata 832 can be analyzed to detect a partial or completely pluggedstatus within a nozzle 802. For example, historical data analyzer 840can compare contemporaneously received nozzle data for a nozzle 802 tohistorical nozzle data 832 and detect a statistically significantdifference. Additionally, comparative data analyzer 860 can comparenozzle data 832 from a single nozzle, to a known-good standard. Forexample, the known-good standard can include an average ofcontemporaneously received data 832 from all nozzles 802. Additionally,the known-good standard can include a standard provided from amanufacturer.

Based on a comparison, for example from historical data analyzer 840 orcomparative data analyzer 860, plug status detector 850 detects that anozzle 802 is experiencing partial or complete plugging, and generates aplugging indication. The plugging indication is then transmitted bycommunication component 870 to an operator 880, for example through adisplay on the agricultural vehicle, or through a display on a deviceassociated with operator 880. Also, the figures show a number of blockswith functionality ascribed to each block. It will be noted that fewerblocks can be used so the functionality is performed by fewercomponents. Also, more blocks can be used with the functionalitydistributed among more components.

It should also be noted that the different examples described herein canbe combined in different ways. That is, parts of one or more examplescan be combined with parts of one or more other examples. All of this iscontemplated herein.

Example 1 is an agricultural sprayer, comprising:

-   -   at least one nozzle configured to receive a fluid and direct        atomized fluid to an agricultural surface in a dispersal area;    -   a radio-frequency (RF) transmitter disposed to generate an RF        signal that passes through the dispersal area, wherein the RF        signal is detectably changed when interacting with droplets of        the atomized fluid;    -   a first RF receiver disposed to receive the RF signal after the        RF signal passes through the dispersal area, the first RF        receiver providing an output indicative of the RF signal; and    -   a controller coupled to the first RF receiver and configured to        detect plugging of the at least one nozzle based on the output        of the first RF receiver.

Example 2 is the agricultural sprayer of any or all previous exampleswherein the at least one nozzle comprises a plurality of nozzles.

Example 3 is the agricultural sprayer of any or all previous examplesand further comprising a second RF receiver, wherein the first RFreceiver is disposed to receive the RF signal after passing through thedispersal area of a first nozzle of the plurality of nozzles, and thesecond RF receiver is disposed to receive the RF signal after passingthrough the dispersal area of a second nozzle of the plurality ofnozzles.

Example 4 is the agricultural sprayer of any or all previous exampleswherein the controller is configured to detect plugging by comparing theoutput of the first RF receiver to an output of the second RF receiver.

Example 5 is the agricultural sprayer of any or all previous exampleswherein the controller is configured to detect plugging by comparing theoutput of the first RF receiver to default data.

Example 6 is the agricultural sprayer of any or all previous exampleswherein the plurality of nozzles are part of a multi-nozzle assembly.

Example 7 is the agricultural sprayer of any or all previous examplesand further comprising a plurality of multi-nozzle assemblies.

Example 8 is the agricultural sprayer of any or all previous exampleswherein the nozzles are spaced apart along a boom.

Example 9 is the agricultural sprayer of any or all previous exampleswherein the controller is configured to provide an indication ofplugging based on the detection.

Example 10 is the agricultural sprayer of any or all previous exampleswherein the controller is configured to engage a different nozzle basedon the detection.

Example 11 is the agricultural sprayer of any or all previous exampleswherein the RF signal has a frequency in the range from about 7 GHz toabout 55 GHz.

Example 12 is an agricultural sprayer, comprising:

-   -   a first multi-nozzle assembly having a multi-nozzle body and a        plurality of nozzles coupled to the multi-nozzle body, each of        the plurality of nozzles being separately actuatable and each        having a respective dispersal area;    -   a first radio-frequency (RF) transmitter disposed to generate a        first RF signal that passes through the dispersal area of a        first nozzle of the plurality of nozzles, wherein the first RF        signal is detectably changed when interacting with droplets of        the atomized fluid in the dispersal area of the first nozzle of        the plurality of nozzles;    -   a second RF transmitter disposed to generate a second RF signal        that passes through the dispersal area of a second nozzle of the        plurality of nozzles, wherein the second RF signal is detectably        changed when interacting with droplets of the atomized fluid in        the dispersal area of the second nozzle of the plurality of        nozzles;    -   an RF receiver disposed to receive the first and second RF        signals and provide an output indicative thereof; and    -   a controller coupled to the RF receiver and configured to detect        plugging of the at least one nozzle based on the output of the        RF receiver.

Example 13 is the agricultural sprayer of any or all previous exampleswherein the controller is configured to detect plugging by comparing theoutput of the RF receiver when detecting the first RF signal to theoutput of the RF receiver when detecting the second RF signal.

Example 14 is the agricultural sprayer of any or all previous exampleswherein the controller is configured to detect plugging by comparing theoutput of the RF receiver to default data.

Example 15 is the agricultural sprayer of any or all previous exampleswherein the RF signal has a frequency in the range from about 7 GHz toabout 55 GHz.

Example 16 is the agricultural sprayer of any or all previous exampleswherein the controller is configured to provide an indication ofplugging based on the detection.

Example 17 is the agricultural sprayer of any or all previous exampleswherein the controller is configured to automatically disable a nozzleassociated with plugging and activate a different nozzle of theplurality of nozzles.

Example 18 is the agricultural sprayer of any or all previous exampleswherein the first and second nozzles are disposed diametrically oppositeone another on the multi-nozzle body.

Example 19 is a method of detecting plugging in a nozzle of anagricultural sprayer, the method comprising:

-   -   generating a radio-frequency signal that passes through a        dispersal area of the nozzle;    -   receiving the radio-frequency signal after the radio-frequency        signal passes through the dispersal area of the nozzle and        comparing attenuation of the received signal with a reference;        and    -   generating an indication of plugging based on the comparison.

Example 20 is the method of any or all previous examples wherein thereference is a radio-frequency signal that passes through a dispersalarea of a different nozzle.

Although the subject matter has been described in language specific tostructural features and/or methodological acts, it is to be understoodthat the subject matter defined in the appended claims is notnecessarily limited to the specific features or acts described above.Rather, the specific features and acts described above are disclosed asexample forms of implementing the claims.

What is claimed is:
 1. An agricultural sprayer, comprising: at least onenozzle configured to receive a fluid and direct atomized fluid to anagricultural surface in a dispersal area; a radio-frequency (RF)transmitter disposed to generate an RF signal that passes through thedispersal area, wherein the RF signal is detectably changed wheninteracting with droplets of the atomized fluid; a first RF receiverdisposed to receive the RF signal after the RF signal passes through thedispersal area, the first RF receiver providing an output indicative ofthe RF signal; and a controller coupled to the first RF receiver andconfigured to detect plugging of the at least one nozzle based on theoutput of the first RF receiver.
 2. The agricultural sprayer of claim 1,wherein the at least one nozzle comprises a plurality of nozzles.
 3. Theagricultural sprayer of claim 2, and further comprising a second RFreceiver, wherein the first RF receiver is disposed to receive the RFsignal after passing through the dispersal area of a first nozzle of theplurality of nozzles, and the second RF receiver is disposed to receivethe RF signal after passing through the dispersal area of a secondnozzle of the plurality of nozzles.
 4. The agricultural sprayer of claim3, wherein the controller is configured to detect plugging by comparingthe output of the first RF receiver to an output of the second RFreceiver.
 5. The agricultural sprayer of claim 1, wherein the controlleris configured to detect plugging by comparing the output of the first RFreceiver to data selected from the group consisting of default data,historical data, and information about all nozzles.
 6. The agriculturalsprayer of claim 2, wherein the plurality of nozzles are part of amulti-nozzle assembly.
 7. The agricultural sprayer of claim 4, andfurther comprising a plurality of multi-nozzle assemblies.
 8. Theagricultural sprayer of claim 2, wherein the nozzles are spaced apartalong a boom.
 9. The agricultural sprayer of claim 1, wherein thecontroller is configured to provide an indication of plugging based onthe detection, wherein the indication is selected from the groupconsisting of an audible indication, a visual indication, an LEDindication, and a mobile indication.
 10. The agricultural sprayer ofclaim 1, wherein the controller is configured to engage a differentnozzle based on the detection.
 11. The agricultural sprayer of claim 1,wherein the RF signal has a frequency in the range from about 7 GHz toabout 55 GHz.
 12. An agricultural sprayer, comprising: a firstmulti-nozzle assembly having a multi-nozzle body and a plurality ofnozzles coupled to the multi-nozzle body, each of the plurality ofnozzles being separately actuatable and each having a respectivedispersal area; a first radio-frequency (RF) transmitter disposed togenerate a first RF signal that passes through the dispersal area of afirst nozzle of the plurality of nozzles, wherein the first RF signal isdetectably changed when interacting with droplets of the atomized fluidin the dispersal area of the first nozzle of the plurality of nozzles; asecond RF transmitter disposed to generate a second RF signal thatpasses through the dispersal area of a second nozzle of the plurality ofnozzles, wherein the second RF signal is detectably changed wheninteracting with droplets of the atomized fluid in the dispersal area ofthe second nozzle of the plurality of nozzles; an RF receiver disposedto receive the first and second RF signals and provide an outputindicative thereof; and a controller coupled to the RF receiver andconfigured to detect plugging of the at least one nozzle based on theoutput of the RF receiver.
 13. The agricultural sprayer of claim 12,wherein the controller is configured to detect plugging by comparing theoutput of the RF receiver when detecting the first RF signal to theoutput of the RF receiver when detecting the second RF signal.
 14. Theagricultural sprayer of claim 12, wherein the controller is configuredto detect plugging by comparing the output of the RF receiver to defaultdata.
 15. The agricultural sprayer of claim 12, wherein the RF signalhas a frequency in the range from about 7 GHz to about 55 GHz.
 16. Theagricultural sprayer of claim 12, wherein the controller is configuredto provide an indication of plugging based on the detection.
 17. Theagricultural sprayer of claim 12, wherein the controller is configuredto automatically disable a nozzle associated with plugging and activatea different nozzle of the plurality of nozzles.
 18. The agriculturalsprayer of claim 12, wherein the first and second nozzles are disposeddiametrically opposite one another on the multi-nozzle body.
 19. Amethod of detecting plugging in a nozzle of an agricultural sprayer, themethod comprising: generating a radio-frequency signal that passesthrough a dispersal area of the nozzle; receiving the radio-frequencysignal after the radio-frequency signal passes through the dispersalarea of the nozzle and comparing attenuation of the received signal witha reference; and generating an indication of plugging based on thecomparison.
 20. The method of claim 19, wherein the reference is aradio-frequency signal that passes through a dispersal area of adifferent nozzle.